99s. rough idle during cold start. once it gets going, it is fine. warm/hot starts are fine. this just happened right after a massive rainstorm here. worst flooding ever. car had a soaked driver's side floor mat, the carpet underneath was wet, but only where the sides of the floormat were, and a bit in the middle. appears that the water came in from up top, and the floormat caught most of it. i cannot find any entry path, no drips, etc. i doubt it can ever be duplicated. it is all dry now. afaik, car not driven thru deep water. ce lite was flashing, code pulled, #5. i changed out the coil and the plugs. erased the lite, it has not come back, but it still has rough idle at cold start. i am thinking the pcm dont know it needs to be in cold start mode, so i am thinking coolant temp sensor. where does it live? from the manual, it looks like it is in the front of the engine, between the banks. also, it looks like a special socket is needed to remove it. who has done this, and what will i need?

followup: i just went out this morning, and the problem is gone. while i would still like to know about changing the sensor, i am now thinking it was something else. either something got wet, and is now dried out(good luck finding out WHAT), or, i am leaning towards water in the fuel. since fuel is lighter, water will sink to the bottom of the fuel tank. when it sits for a while, water can form a puddle at the pickup, and when the car is first started, some water will go thru the fuel lines. after driving, the fuel is agitated, so the water is now dispersed. i threw in a bottle of drigas yesterday, just in case.